It doesn’t directly answer this need, but I think the reality is most viewers aren’t on PeerTube at all, they’re on Mastodon. And they’re using whatever Mastodon client to watch PeerTube videos. Some clients support direct viewing and others will just show up as a link taking them into the browser.
A dedicated app would be a gamechanger for a very very small number of people, but until that number grows and while everyone is just using other platforms to watch videos, I can understand why nobody’s gone to the effort.